Self-indicating clamping bolt

ABSTRACT

A bolt for securing together electrical connectors comprising a shank having a reduced diameter section, a first and second head mounted on said shank and spaced apart by the reduced diameter section, said second head being shearable at a predetermined torque, and a colored band carried by said first head for visually indicating the relative adjustment of said bolt.

United States Patent 1 1 3,561,317

[72] inventor John C. Rowell 2,824.48! 2/1958 Johnson 4 85/62 Middlebury, Conn- 3,174,383 3/1965 HeiL 85/61 [21] Appl. No. 813,549 3,224,316 12/1965 Grikscheit et a1... 85/62 [22] Filed Apr. 4, 1969 3,383,974 5/1968 Dahl 85/62 [45] Patented Feb. 9, 1971 B C FOREIGN PATENTS 73 Assi ee Anaconda American rass ompany l 1 a a corporation of Connecticut 898,026 6/1962 Great Britain 85/61 Primary ExaminerMarion Parsons, Jr. An0meyPennie, Edmonds, Morton, Taylor and Adams [54] SELF-INDICATING CLAMPING BOLT 7 Claims, 4 Drawing Figs.

[52] US. Cl 85/61, 85/9 [5 Int. A bolt for ecuring together electrical connec- 0f 62, tors comprising a shank having a reduced dimneter section a v 9 first and second head mounted on said shank and spaced apart by the reduced diameter section, said second head being [56] References cued shearable at a predetermined torque, and a colored band car- UNITED STATES PATENTS ried by said first head for visually indicating the relative ad- 1,184,173 5/1916 Gehring 85/45 justment of said bolt.

PATENTED-FEB 9 I97! FIG.4

INVENTOR JOHN c. ROWELL ATTORNEYS SELF-lNDlCATING CLAMPING BOLT BACKGROUND OF THE INVENTION The invention relates generally to bolts but, in particular, to a bolt for securing together electrical connectors and has for its principle object a means for determining, by visual inspection, the relative adjustment of said bolt.

In the operation of complex electrical equipment where dependable operation depends on proper contact of a large number of electrical connections, in many cases extending literally into the thousands, it has been the practice in the past to rely on the thoroughness of the workman to effect the proper connections in all of the desired places during the manufacturing stage. when a breakdown does occur the manufacturer is oftentimes required to spend thousands of hours and dollars in tracing circuits only to find a loose connection left by a careless electrician.

These electrical connections are usually accomplished by means of a small bolt or screw having a threaded portion which is inserted into a threaded socket which communicates electrically with another portion of the particular circuit. An electrical wire or other suitable electrical conduit is then attached by any suitable means to the bolt between the head of the bolt and its socket after which the bolt is tightened into its socket to effect clamping of the electrical conduit therebetween.

It will be appreciated that a less than fully tightened bolt will increase the probability of separation of the various electrical connections thereby disrupting, and in some cases preventing, the proper functioning of the particular circuit associated with the disjunction.

This type of bolted connection is highly desirable from the standpoint of assembling the various circuits in the manufacturing operation in that the required connections can be made rapidly with very little skill and effort. However, upon failure of a particular circuit, the bolted connection as described above provides no alternative to the actual manual check of all connections to determine which connections, if any, are the cause of the malfunction. As mentioned above, the procedure is tedious, and time-consuming.

It is therefore a principle object of the invention to provide a bolt-actuated clamping device which is equipped with a means for visually inspecting the various connections to determine which, if any, of the connections has been broken. Accordingly, the subject matter of this invention entirely eliminates the need for manually checking each individual connection. In addition, such visual inspection permits rapid identification of the faulty connection with consequent savings both in time and money.

SUMMARY OF THE INVENTION In accordance with the teachings of the present invention, there is provided a bolt of economical and simple construction and one which can be used for effecting the proper connection of various elements of an electrical circuit. In construction, the bolt includes an elongated shank threaded at one end and having a reduced diameter section at the other end. The shank is constructed of metal and has attached thereto a first head and a second head in a spaced relationship from each other. The first head is formed integral with the larger diameter section and the second head is formed integral with a reduced diameter section. The gripping surface of the first head carries a colored band of suitable material, said band being adapted to be sheared away from said first head upon the application of suitable force, say, for instance, when a socket head wrench is applied to remove or loosen the bolt. The second head is provided with a coating of any suitable substance having a color different than that of said band. With this arrangement,

a predetermined torque applied to the bolt by turning the second head, will, because of the reduced tapered diameter.

diameter of the tapered shank section. As a result, the colored band carried by the first head can be visually seen for purposes of inspecting the security of the various connections, all of which will become abundantly clear by reference to the following portion of the specification in which a detailed description of the invention appears.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevation view of the bolt;

FIG. 2 is a sectional view taken along the line 2-2 of FIG. 1;

FIG. 3 is a side elevational view of the bolt showing its relationship to the socket, tightening wrench and electrical connector;

FIG. 4 is a side elevation view of a bolt whose inner and outer heads are the same size.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 3 the electrical conduit 1 is to be clamped into electrical contact with a threaded socket 2 to which is attached in electrical communication by any suitable means, say by soldering, a second electrical conduit .3 leading to another junction (not shown) of the particular circuit. For purposes of illustration only, the socket 2 is shown imbedded in a circuit board or panel member 4.

The subject matter of the invention is concerned with a bolt, indicated generally at 10, for effecting the desired clamping action. The bolt is made of an electrically conductive material, such as a suitable metal, and comprises a shank indicated generally by reference numeral 20, one end of which is threaded as at 5 so as to be adapted for internal connection with the threaded socket 2.

The shank 20 is quite elongated and is provided with a tapered neck portion 6 having a diameter smaller than the uniform diameter of the shank adjacent its threaded end 5. It should be noted that the threaded end 5 of the shank 20 could, in fields of use other than that of electrical connectors, accommodate an ordinary nut, in which case the shank could be any length depending on the particular application.

Formed integral with the larger diameter section 7 of the shank 20 is a head 8 provided with a gripping surface 9 which, by preference, is hexagonal, but may be of any other suitable configuration.

Spaced apart from inner head 8 and formed integral with the reduced diameter section 6 of the shank 20 is a second head 11, which may be smaller than inner head 8 and which preferably has a hexagonal gripping surface 12 but may, like inner head 8, be of any other suitable configuration, say for instance, square or octagonal. The purpose in providing for outer head 11 is to assure that the force of wrench 14 will be initially applied only to outer head 11. This may be accomplished by making outer head 11 smaller than inner head 8, thus requiring a different size wrench to turn inner head 8. As shown in FIG. 3, a wrench conforming to the size of the outer head 11 will be blocked from turning inner head 8 by the larger size of inner head 8 despite the fact that the depth of the wrench socket might otherwise permit it.

On the other hand, outer head 11 may be made the same size as inner head 8, as shown in FIG. 4. However, the depth of the socket in wrench 14 should be shallow so as not to engage inner head 8. If a deep socket wrench is used, colored band 15 on inner head 8 will be destroyed and thereby signal misuse.

In the preferred form of the invention as shown most clearly in FIG. 3, it will be recognized that the shank 20 is capable of withstanding varying amounts of torque at difi'erent points along its length, the weakest point in any torque applying operation being located at point 13 where section ,6 of shank 20 has its smallest diameter. Thus, inner head 8 will withstand appreciably more applied torque than will outer head 11.

In accordance with these observations it can be readily determined by calculation or experimentation the amount of torque necessary to effect an adequate tightening of the bolt from which can be determined the proper diameter and taper for shank section 6, that is, the diameter of the reduced section is such as to cause the reduced section to yield at the torque value equal to or slightly in excess of the torque necessary for proper tightening of the bolt 10. The distance between heads 8 and 11 should advantageously be not greater than the axial length of either head, but may be sufficiently greater than said length when necessary to insure that the head 8 will clear the end of a conventional socket head wrench l4 placed in gripping relationship over the head 11.

As shown in FIG. 1, at least one portion of gripping surface 9 of inner head 8 carries a thin colored band 15, which in accordance with the preferred embodiment is made of a suitable plastic material. The band is affixed to the gripping surface 9 in any suitable manner so as to effect a rather weak bond between said band and said gripping surface. For instance, the preferred embodiment of this invention contemplates depositing a small quantity of an adhesive or tacking substance on the inner portion 16 of the band and subsequently pressing the band into engagement with said gripping surface to effect the desired engagement. In an alternative embodiment of the invention the band can be made of a resilient plastic material to form, essentially a hoop which is held in place around the gripping surface by the radial forces created by the resiliency of the band.

With this arrangement, separation of the band from the head 8 is quite readily effected by application of a suitable axial force applied to said band. For example, the force exerted when a socket wrench is applied to the head 8 to loosen or remove the bolt 10, would be sufficient to accomplish this separation.

As indicated by the shaded portion of FIG. 1, outer head 1 1 is provided with a coating 18 having a color different from that of the plastic band 15. 1n the preferred embodiment of this invention, the coating material consists of a paint or lacquer which is usually applied by means of an appropriate spraying technique. However, any other substance and method application can be used without departing from the spirit of this invention.

The colored band 15 and the colored coating 18 on heads 8 and 11 respectively serve in combination and individually to facilitate the visual inspection of the electrical connections to which the subject matter of this invention is intended to be applied, the utilization of which can be best understood by reference to the following portion of the specification which contains a description of the operation of the bolt described hereinbefore. Assume for purposes of illustration that the plastic band 15 is colored bright blue and the head 11 is colored bright red.

A bolt of the type described above and having the proper torque value is first inserted into the socket 2 and rotated so as to engage a small portion of the corresponding threads of the bolt 10. The exposed end 19 of the electrical wire 1 is then placed in contact with the larger diameter section 7 of the shank 20, for instance, by curling said end into a hook shape around said shank, in substantially the same manner as indicated in FIG. 3.

The bolt 10 is .then advanced axially into the socket 2 by turning the head 11 clockwise with an appropriate socket head wrench 14, as depicted in phantom in FIG. 3 until head 8 abuts against the flanged mouth 21 of the socket 2. The workman then continues to apply increased torque either manually or with the aid of a suitable automatic torque wrench (usually air or electrically operated) until the weaker portion of said bolt shears freeing the head 11, at which point, as discussed above, the bolt 10 will be properly tightened thereby firmly clamping the wire 1 into electrical contact with the socket 2 between it and the head 8.

When and if a breakdown occurs, the electrician who must trace the circuitry, will be alerted to an improperly tightened bolt by the visual impression of a redcolor at any of the various connective junctions. The presence of the red color indicates that the head 11 has not been sheared away which in turn indicates that the bolt 10 was initially left untightened.

On the other hand, if the inspector sees the color blue at any of the various connections, he can be assured that the bolt was properly tightened initially and remains in that condition. This is true because the shearing away of the red head 11 exposes the blue band 15 carried by the-head 8 to his view, and the head 11 could only be sheared away if the proper torque was applied to it initially.

If the inspector observes neither the red head 11 nor the blue band 15 he is promptly alerted to the fact that the bolt 10 has somehow been tampered with subsequent to the initial tightening operation. This is true because as discussed above, the blue band 15 will be sheared away from the gripping surface 9 of the head 8 upon any attempt to loosen or remove the bolt subsequent to initial tightening.

Thus, in summary, it will be appreciated that the subject matter of this invention provides a new and useful bolt for securing together electrical connectors. The visual inspection means described above provides a rapid and efiicient technique for locating faulty connections which may arise at the various junctions of the circuit. The manual check of all connections, heretofore necessary, is entirely obviated with resultant savings in both time and money. in addition, the structure of the bolt described herein is exceedingly simple in construction and easy to manufacture.

The above description of the present invention has been made with reference to the preferred embodiment; however, it is to be understood that various changes may be made thereto without departing from the spirit of the invention and the scope of the appended claims.

I claim:

1. in a bolt of the type for clamping together electrical connectors including an elongated shank having a threaded portion at one end, a first head integrally connected to the other end of the shank portion forming an extension of the shank adjacent to the first head and having a diameter reduced from that of the shank, a neck portion forming an extension of the shank adjacent to the first head, a second head spaced apart from the first head and connected integrally to the neck portion, the improvement in combination therewith comprising indicating means secured to a gripping surface of the first head, the indicating means remaining visible when the bolt is first tightened to a torque which is sufficient to shear the neck portion at its reduced diameter and the indicating means being adapted to be sheared away from the gripping surface of the first head upon subsequent application of torque to the first head.

2. A bolt according to claim 1 wherein the indicating means comprises a colored band secured to at least a portion of the gripping surface of the first head.

3. The bolt of claim 1 wherein the band is made of a plastic material.

4. The bolt of claim 3 wherein the second head is provided with a coating having a color different from that of the band.

5. The bolt according to claim 4 wherein the coating is paint.

6. The bolt according to claim 5 wherein the first head is a hexhead.

7. The bolt according to claim 6 wherein the second head is a hexhead. 

1. In a bolt of the type for clamping together electrical connectors including an elongated shank having a threaded portion at one end, a first head integrally connected to the other end of the shank portion forming an extension of the shank adjacent to the first head and having a diameter reduced from that of the shank, a neck portion forming an extension of the shank adjacent to the first head, a second head spaced apart from the first head and connected integrally to the neck portion, the improvement in combination therewith comprising indicating means secured to a gripping surface of the first head, the indicating means remaining visible when the bolt is first tightened to a torque which is sufficient to shear the neck portion at its reduced diameter and the indicating means being adapted to be sheared away from the gripping surface of the first head upon subsequent application of torque to the first head.
 2. A bolt according to claim 1 wherein the indicating means comprises a colored band secured to at least a portion of the gripping surface of the first head.
 3. The bolt of claim 1 wherein the band is made of a plastic material.
 4. The bolt of claim 3 wherein the second head is provided with a coating having a color different from that of the band.
 5. The bolt according to claim 4 wherein the coating is paint.
 6. The bolt according to claim 5 wherein the first head is a hexhead.
 7. The bolt according to claim 6 wherein the second head is a hexhead. 